1. Field of the Invention
The present invention relates to a holder for supporting a headrest, or the so-called “headrest holder”, by means of which the headrest is supportively mounted on a top of seat back of automotive seat, the holder itself being able to be supported on an upper region of seat back frame and being so configured to allow a stay of the headrest (or headrest stay) to be inserted and retained therein for the purpose of securing the headrest in position upon the seat back. In particular, the invention is directed to the headrest holder of this kind which effectively prevents wobbling and rattling of a headrest stay therein as well as of the headrest holder itself in a support bracket fixed to the upper region of seat back frame.
2. Description of Prior Art
In general, a headrest holder stated above comprises a head portion and a cylindrical body portion extending from the head portion, the cylindrical body portion being adapted to permit a stay of headrest to be inserted and retained therein.
As one of the hitherto problems found in the headrest holder, the headrest stay, even when securely retained in the headrest holder, is prone to wobbling and rattling due to a clearance between the outer surface of the headrest stay and the inner surface of the headrest holder. Likewise, the headrest holder per se, even when securely fitted in a support bracket fixed to a seat back frame, is prone to wobbling and rattling due to a clearance between the outer surface of, the headrest holder and the inner surface of the support bracket.
Solution to this problem is for example found from the Japanese Laid-Open Patent Publication No. 11-89665 (or JP 11-89665 A) which discloses a headrest holder having resilient tension pieces defined in the cylindrical body portion thereof, wherein the tension pieces are each so configured to resiliently provide a pressure in a direction inwardly of the cylindrical body portion. According to the JP 11-89665 A, a first pair of the tension pieces and a second pair of the tension pieces are formed in the cylindrical body portion in an opposedly facing fashion at a same level. Hence, when the headrest stay is inserted in the cylindrical body portion of such holder, those first and second pairs of tensions pieces contact and press on both two opposite surfaces of the headrest stay, thereby applying a pressure thereto, so that the headrest stay is retained therebetween. More specifically, each of the tension pieces is formed with a projected region in the inner surface thereof and also formed in the outer surface thereof with a recessed region at a point corresponding to that projected region. The projected region is of a substantially arcuate shape in cross-section and projects inwardly from the inner surface of the headrest holder towards an axial center of the headrest holder. On the other hand, the recessed region, opposite to the projected region, has two sharply pointed projections that project outwardly from the outer surface of the headrest holder.
The thus-formed headrest holder is first fitted in a support bracket fixed to a seat back frame, prior to the headrest stay being inserted in the holder. Then, when the headrest stay is inserted in that headrest holder, the outer surface of the headrest stay presses all the afore-said projected regions of the tension pieces, while simultaneously all the afore-said two sharply pointed projections of the recessed regions of the tension pieces are brought to pressed contact with the inner surface of the support bracket. Under such state, all the tension pieces act to apply a pressure to both of the headrest stay and support bracket, so that the headrest stay is retained in the holder, while the headrest holder retained in the support bracket as well. Ostensibly, this arrangement provides a prevention of the above-stated wobbling and rattling of headrest stay and headrest holder.
But, in such prior art, all the tension pieces are disposed collectively at a same level in one localized area of the body portion of the headrest holder. As a result thereof, when a headrest stay has been inserted in that holder, a pressure is applied from the tension pieces intensively to one localized area of the headrest stay, which may result in the headrest stay being inclinable relative to the tension pieces within the inner bore of the headrest holder's body portion, because the tension pieces as a whole only provide one support point to the headrest stay. Consequently, it is highly possible that the headrest stay will be wobbled and rattled in the headrest holder. Further, the configuration of each of the tension pieces, i.e. the arcuately projected and recessed regions defined in the tension piece, is extremely complicated, which requires a high expertise of forming the headrest holder and further increases costs involved. Of course, the first pair of tension pieces and the second pair of tension pieces may be arranged in the upper and lower areas of the holder's cylindrical body portion, respectively, in an attempt to positively prevent wobbling and rattling of the headrest stay in the holder, but forming such configuration of headrest holder will make its structural design more complicated and also will require increased forming costs as well as careful technical skills.